Fix build of Haskell Report

Turns out that special care needs to be taken when escaping `|`s in
`\index{}`. See also
http://tex.stackexchange.com/questions/176931/how-to-escape-character-in-index

http://tex.stackexchange.com/questions/106159/why-i-shouldnt-load-pdftex-option-with-hyperref

Make sure that `make clean` is more thorough, and create ht/libs on the
fly if needed.

Also modernised the Haskell a little

It's not part of the report, and hasn't been touched for 10 years.

Thanks: S D Swierstra <doaitse@uu.nl>